Overload spring structure

ABSTRACT

An overload spring assembly for a vehicle, including two coil springs or spring sections interposed between the sprung and unsprung masses of the vehicle, with one of the two springs being stiffer than the other, and with the springs being ineffective to assist the main suspension system under normal load conditions, but being movable into supporting relation under a predetermined overload condition. Stops associated with the springs, and preferably carried by a shock absorber within the interior of the springs, cause the springs when they do become effective to produce first a soft supporting action, and then a stiffer action dependent only upon the characteristics of the stiffer spring, with the stops preferably also serving in an extended or rebound condition to resiliently limit the separation of the sprung and unsprung masses.

United States Patent Primary Examiner-James B. Marbert Attorney-WilliamP. Green ABSTRACT: An overload spring assembly for a vehicle, includingtwo coil springs or spring sections interposed between the sprung andunsprung masses of the vehicle, with one of the two springs beingstifier than the other, and with the springs being ineffective to assistthe main suspension system under normal load conditions, but beingmovable into supporting relation under a predetermined overloadcondition. Stops associated with the springs, and preferably carried bya shock absorber within the interior of the springs, cause the springswhen they do become effective to produce first a soft supporting action,and then a stifier action dependent only upon the characteristics of thestiffer spring, with the stops preferably also serving in an extended orrebound condition to resiliently limit the separation of the sprung andunsprung masses.

I OVERLOAD SPRING STRUCTURE CROSS REFERENCE TO RELATED APPLICATIONCertain features of the apparatus disclosed in the present applicationare shown in my copending application entitled Variable StiffnessSuspension System," Ser. No. 768,249, filed of even date herewith.

BACKGROUND OF THE INVENTION {produced a very stiff ride, that is, one in,which rough and abrupt movements caused by irregularities in the roadare transmitted to the body of the vehicle with very little cushioningeffect. These rough riding qualities have been encountered so long asthe overload spring assembly is mounted on the vehiclein a condition tosupport overloads, and even though the load actually in the vehicle at aparticular time is very light.

SUMMARY OF THE INVENTION In an overload spring arrangement constructedin accordance with the present invention, the smoothness and quality ofthe ride may be completely unafi'ected by the overload spring assemblyunder normal or light load conditions, so that under such conditions thesame riding qualities are attained as would be produced by the mainsuspension system of the vehicle if the overload assembly were notpresent. When an overload condition occurs, however, the overload springassembly automatically comes into effect to assist in supporting theweight of the sprung mass. Further, the assembly is designed to, at thattime, first produce a relatively soft or weak supporting effect forsupplementing the main suspension system rather lightly, and then uponfurther downward movement of the sprung mass produce a stiffer assistingeffect.

' Structurally, the assembly includes tow springs or spring sections,one of which is stiffer than the other, with the springs being soconstructed and positioned. that under normal load conditions they areineffective to assist in supporting the sprung mass, whereas upon anincrease in load applied to the vehicle, the lighter or weaker springfirst compresses, followed by compression of the stiffer spring toattain maximum support. Conversion between the light spring and stiffspring supporting condition is attained by provision of stop shoulders'which limit compression of the weaker or softer spring. Additionally,upon excessive upward bounce or rebound of the sprung mass, other stopshoulders become effective to actually support the unsprung mass fromthe sprung mass through the stiffer of the two springs. Certain of thestop shoulders may be carried by a shock absorber located within thespring assembly, and connected to the sprung and unsprung masses in amanner resisting relative movement thereof.

BRIEF DESCRIPTION OF THE DRAWING The above and other features andobjects of the invention will be better understood from the followingdetailed description of the typical embodiment illustrated in theaccompanying drawing, in which:

FIG. 1 is a fragmentary diagrammatic representation of a portion of amotor vehicle having an overload spring assembly constructed inaccordance with the invention;

FIG. 2 is a greatly enlarged fragmentary view showing the overloadspring assembly of FIG. I;

.1 FIG. 3 shows fragmentarily the assembly of FIG. 2 under a slightoverload condition; and

FIG. 4 is a horizontal section taken on line 4-4 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, Ihave illustrated in that FIG., one of the four wheels 10 of anautomobile or other motor vehicle,

having a conventional suspension system of any known type forresiliently supporting a body or sprung mass 11 from a wheel-carrying orwheel-connected unsprung mass 12. The conventional suspension system mayfor example include four coil springs 13 located near the four wheelsrespectively of the vehicle, for resiliently supporting the sprung massI I at its corners. This suspension system, under normal loadconditions, supports the sprung mass in the normal position illustratedin FIGS. I and 2, with the sprung mass being movable downwardly towardand relative to unsprung mass I2 and wheels 10 upon the imposition of anoverload to the vehicle.

In association with the two rear wheels respectively of the vehicle,there are provided two overload coil spring assemblies I4, for assistingthe main suspension springs 13 in supporting the sprung mass underoverload conditions. If desired, and if permitted by the structure ofthe front wheels and their suspension, two additional overload coilspring assemblies, of the same type shown at in FIGS. I and 2, may beprovided in association with the front wheels.

As seen best in FIG. 2, each of the overload spring assemblies includesan upper coil spring 15 which is relatively stiff and strong and has arelatively high spring rate (pounds per inch of compression) and asecond and softer spring 16, having a lower spring or ride rate. Both ofthese springs 15 and 16 may be centered about a common vertical axis I7,with the lower spring preferably being of smaller'diameter than theupper spring about axis 17, and normally also being formed of a smallersize wire.

The'upper end of upper stiff spring 15 has a top turn 18 which, insteadof advancing helically as dothe other turns of the spring, extendsannularly about axis I7, and transversely of that axis. Spring 15 issecured to the vertically movable sprung mass 1] of the vehicle by aclamping element I9, which is received at the undersideof theillustrated portion of the sprung mass, and which contains an annularrecess 20 for receiving turn I8 of spring l5 and clamping it upwardlyagainst the horizontal undersurface of sprung element 11, in fixedposition relative thereto. Screws 21 secure the clamping element I9 tothe sprung mass, as illustrated.

Similarly, the lower end turn 22 of bottom soft spring l6-is shaped toextend annularly rather than helically about axis 17, and thereforetransversely of that axis, and is secured in fixed position relative tothe unsprung mass 12 by a clamping element 23, containing an annularrecess 24 for receiving the turn 22 of spring 16, with screws 25securing parts 23 and 12 together. As will be apparent, clampingelements 19 and 23 of course contain openings through which theassociated springs extend as they advance axially from within therecesses 20 and 24 to the underside of clamping element I9 and the upperside of clamping element 23.

At its lower end, the stiff spring 15 has another transverse annularturn 26, which rigidly carries an annular stop shoulder or stop element27, typically formed of an appropriate metal annularly welded orotherwise secured to the turn 26. This stop shoulder or flange 27 may ineffect be increased in axial thickness by provision of two annular shims28 and 29, which are detachably secured to the underside and the upperside respectively of element 27 by screws 30 or other fastening means,and each of which may be formed of two separate semicircular segments(FIG. 4) to facilitate their removal when desired.

The upper end turn 31 of the soft spring 16 is disposed transversely ofaxis I7, and annularly thereabout, and is of a diameter corresponding toa radially outer portion of shoulder element 27 and its shims 28 and 29,to be engageable with the horizontal undersurface of element 27 whenshim 28 is detached therefrom. The springs and other parts are sodesigned that, when the sprung mass or body II of the vehicle is loadednormally, that is, with no excess weight in or on the vehicle, upperturn 31 of spring I6 is spaced vertically from the undersurface of stopelement 27, or from the undersurface of shim 28 if the shim is in use.This vertical spacing is illustrated at d in FIG. 2.

For further coaction with the stop shoulder or element 27 or its shims28 and 29, there are provided two annular upper and lower stop elementsor shoulders 32 and 33, the first of which has an annular undersurface35 disposed transversely of axis 17 for engaging the upper surface ofelement 27 or its shim 29, and the second of which has an upper annularsurface 135 disposed transversely of axis 17 for engaging theundersurface of element 27 or shim 28. These stop elements 32 and 33 aresecured in fixed position relative to the unsprung mass 12, to limit thevertical movement of the element 27 carried at the lower end of spring15. Preferably, stop elements 32 and 33 are carried by the cylinder 36of a shock absorber 37, which is connected between the sprung andunsprung masses. More particularly, cylinder 36 of the shock absorbermay be secured to the unsprung or wheel connected mass 12 by provisionat the lower end of the cylinder of a horizontal laterally projectingannular flange 38, rigidly carried by the cylinder and confined withinthe recess 24 in the clamping element 23. The piston rod 39 of the shockabsorber, which piston rod is of course connected to the usual piston 40contained within cylinder 36, is connected at its upper end rigidly tothe sprung mass 11, as by connection of two clamping nuts 41 and 42 ontoa threaded upper portion of the piston rod.

To now describe the manner of operation of the auxiliary or overloadsprings of the present invention, assume first of all that the sprungmass 11 of the vehicle of FIG. I is carrying only a normal load, andthat the conventional suspension springs 13 of FIG. I therefore supportthe sprung mass 11 in the FIG. 2 position relative to unsprung mass 12.In this condition, the upper turn 31 of the lower soft spring 16 of eachoverload spring assembly is spaced vertically from the underside of shim28, so that the two springs and 16 are completely out of forcetransmitting engagement with one another, and do not assist the mainsuspension system in supporting sprung mass 11. Thus, the ridingcharacteristics of the vehicle are controlled entirely by the normalsuspension system, and the ride is therefore very soft and not stiffenedto any extent whatever by the presence of the overload or auxiliaryspring assemblies 14 on the vehicle. The amount of spacing d between thespring 16 and the shim 28 is such as to enable as much relative verticalmovement of these parts as will usually occur under normal loadingconditions, without bringing spring 16 into actual engagement with shim28. If, now, an increased load is applied to the sprung mass or body 11of the vehicle, this increased weight will overcome main suspensionsprings 13 sufficiently to move the sprung mass 11 downwardly and bringshim 28 into engagement with the upper turn of spring 16, as indicatedin FIG. 3. In this condition, the two springs 15 and I6-are in effectconnected in series between the sprung mass 11 and unsprung mass 12, tothus add their supporting force to that of main suspension springs 13.As the weight on the vehicle increases, the relatively soft spring 16compresses fairly rapidly, with little or no compression of the upperstifi" spring 15, so that the initial load supporting effect of theauxiliary spring system is a soft additive effect dependent upon thestrength of soft spring 16. If the load increases to a value sufficientto force shim 28 downwardly into contact with stop shoulder 135 carriedby the shock absorber, this engagement prevents further compression ofthe soft spring 16, and thereafter requires compression of the upperstiff spring 15 upon any greater downward movement of sprung mass 11relative to unsprung mass 12. Thus, the support afforded by the overloadspring assembly converts automatically from a soft resilient support toa stiffer support, to provide the relatively great force necessary tosupport the heavy load of the vehicle. Upon a subsequent decrease inload, the auxiliary spring system of course converts automatically in areverse direction through the three different conditions which have beendiscussed, consisting of a stiff ride condition in which the full forceof upper spring 15 supports the load, a softer ride condition in whichlower spring 16 is the main effective element, and the FIG. 2 softestand normal condition in which neither of these springs is effective andthe sole support is through the main suspension system 13.

If the wheels of the vehicle strike an irregularity in the road tendingto cause an excessive rebound of sprung mass 11 up wardly relative toand away from unsprung mass 12, stop shoulder element 27 or its uppershim 29 engages upwardly against the undersurface of annular stopelement 32 on the shock absorber, to transmit upward forces directly tothe body of the shock absorber and unsprung mass 12 from the lower endof spring 15, so that further upward separation of mass 11 relative tomass 12 is resisted resiliently by the full force of stiff spring 15(which is in that condition extended axially and resiliently to anincreased length beyond that of its normal or undefonned condition ofFIG. 2). In this way, the illustrated auxiliary spring assemblyeffectively limits and prevents excessive separation of the sprung andunsprung masses.

The shock absorber 37 is desirably of a double-acting type, in which itsfluid within cylinder 36 resists both upward and downward movement ofthe piston 40, to thereby retard both upward and downward movements ofthe sprung mass 11 relative to mass 12, and thereby optimize thefunctioning of the overload spring assembly, and prevent too frequent ortoo rapid conversion of the system between its different suspendingconditions. The positions at which the auxiliary spring system convertsbetween its different conditions may be altered by removal orinstallation of one or both of the shims 28 or 29, or replacement ofshims of different thicknesses, or by mounting stop shoulders 32 and 33in suitable manner for vertical adjustment along shock absorber cylinder36.

Shims 28 and 29 and stops 35 and may all be formed of a suitable rigidmaterial, such as steel or another metal, to produce an abrupt stoppingaction when either shim contacts one of the stops; or, alternatively andpreferably, some or all of these elements 28, 29, 35 and 135 may beformed of an appropriate elastomeric material, such as a fairly hardrubber to cushion the stopping action and enable some resilientlyresisted motion of element 27 after contact of it or one of the shimswith element 35 or 135. In either instance, it is for best resultsdesirable that the stop shoulders completely halt all compression ofspring 16 at a position in which its successive turns are still spacedaxially apart a substantial distance, and are not in direct abuttingengagement with one another, so that except for the limiting actionproduced by engagement of shim 28 or element 27 with stop 135, thespring 16 would be free for further compression.

Iclaim:

I. In a motor vehicle having a main suspension system supporting asprung mass resiliently in a predetermined normal position relative toan unsprung mass; overload apparatus comprising two coil spring sectionsin addition to said main suspension system received operatively and inseries between said sprung and unsprung masses, a first of said springsections being relatively stiff and the second section being relativelysoft, said sections being ineffective to assist in supporting the sprungmass in said normal position thereof but being positioned andconstructed to become effective for such support in series with oneanother when the sprung mass moves downwardly relative to the unsprungmass to an overload position, and shoulder means engageable uponpredetermined further downward movement of said sprung mass relative tosaid unsprung mass beyond said overload position to thereafter supportsaid sprung mass by said stiffer section independently of said softersection.

2. Overload apparatus as recited in claim 1, including shoulder meansengageable in an elevated relative position of said sprung mass toyieldingly resist further relative elevation of said sprung mass by theforce of said stiff spring section and independently of said soft springsection.

3. Overload apparatus as recited in claim 1, including a shock absorberwithin said two spring sections.

tion but are movable into load transmitting relation in said overloadposition of the sprung mass.

6. Overload apparatus as recited in claim 1, in which said springsections are formed separately and have adjacent ends which in saidnormal position are spaced apart but are movable into load-supportingrelation to transmit forces therebetween in said overload position, saidshoulder means including a first stop shoulder carried by said end ofone of said spring sections, and a second stop shoulder engageable bysaid first stop shoulder after predetermined compression of said softspring section to prevent further compression thereof and transmit loadforces between said masses directly through only said stiff springsection.

7. Overload apparatus as recited in claim 1 in which said two springsections are formed separately and have first ends received inload-supporting relation with respect to said two masses respectively,said sections having second ends which in said normal position-arespaced apart but are moveable into load-supporting relation to transmitforces therebetween in said overload position, there being a first stopshoulder carried by said second end of one of said spring sections, anda second stop shoulder engageable by said first stop shoulder afterpredetermined elevation of said sprung mass above said normal positionto yieldingly resist further relative elevation of said sprung mass bythe force of said stiff spring section.

8. Overload apparatus as recited in claim 1 in which said stiff springsection has a first end secured in fixed position to one of saidmasses,,said shoulder means including a shoulder at the opposite end ofsaid stiff spring section, and an additional shoulder carried by theother mass and engageable by said first shoulder in force transmittingrelation after said predetermined relative movement of said twoshoulders.

9. Overload apparatus as recited in claim 1 in which said stiff springsection has a first end connected in fixed position .to one of saidmasses and has a second end which in said normal position is out of loadtransmitting relation with said soft spring section, but is relativelymovable into such load-transmitting relation in said overload position,said shoulder means including a shoulder structure carried by saidsecond end of said stiff section and engageable with two additionalshoulders carried by the other mass to limit relative movement of saidsecond end of the stiff section both upwardly and downwardly.

l0. Overload apparatus as recited in claim 9 including a shock absorberextending vertically within said spring sections and connected atopposite ends to said two masses respectively, and means mounting saidadditional shoulders at spaced locations on said shock absorber.

ll. Overload apparatus as recited in claim 1 including means securing afirst end of said stiff spring section fixedly to one of said masses anda first end of said soft section fixedly to the other mass, saidsections having second ends which in said normal position are out ofload transmitting relation but are movable into such relation in saidoverload position, said shoulder means including a stop shoulderstructure carried by said second end of said stiff spring section, therebeing a shock absorber within the sections and having a cylinder andpiston connectable one to each of said masses, said shoulder meansincluding two stop shoulders carried by said cylinder of the shockabsorber at spaced locations and engageable with said first mentionedstop shoulder structure to transmit forces therefrom directly to thecylinder in two predetermined positions one of which is beneath theposition in which said two spring sections move into load transmittingrelation, and the other of which is above said normal position.

12. In a vehicle having a main suspension system supporting a sprungmass resiliently in a predetermined normal position relative to anupsprung mass; overload apparatus including a stiff coil spring sectionand a softer (2011 spring section received operatively in series betweensaid sprung and unsprung masses, said spring sections being ineffectiveto assist in supporting the sprung mass in said normal position thereofbut being positioned and constructed to become effective for suchsupport in series when the sprung mass moves downwardly relative to theunsprung mass to an overload position, there being shoulder meansengageable in an elevated relative position of said sprung mass abovesaid normal position thereof to yieldingly resist further relativeelevation of said sprung mass by the force of said stiff sectionindependently of said softer section.

1. In a motor vehicle having a main suspension system supporting asprung mass resiliently in a predetermined normal position relative toan unsprung mass; overload apparatus comprising two coil spring sectionsin addition to said main suspension system received operatively and inseries between said sprung and unsprung masses, a first of said springsections being relatively stiff and the second section being relativelysoft, said sections being ineffective to assist in supporting the sprungmass in said normal position thereof but being positioned andconstructed to become effective for such support in series with oneanother when the sprung mass moves downwardly relative to the unsprungmass to an overload position, and shoulder means engageable uponpredetermined further downward movement of said sprung mass relative tosaid unsprung mass beyond said overload position to thereafter supportsaid sprung mass by said stiffer section independently of said softersection.
 2. Overload apparatus as recited in claim 1, including shouldermeans engageable in an elevated relative position of said sprung mass toyieldingly resist further relative elevation of said sprung mass by theforce of said stiff spring section and independently of said soft springsection.
 3. Overload apparatus as recited in claim 1, including a shockabsorber within said two spring sections.
 4. Overload apparatus asrecited in claim 1, including a shock absorber within said two springsections and connected at its opposite ends to said two massesrespectively.
 5. Overload apparatus as recited in claim 1, in which saidspring sections are formed separately and have adjacent ends which insaid normal position are out of load transmitting relation but aremovable into load transmitting relation in said overload position of thesprung mass.
 6. Overload apparatus as recited in claim 1, in which saidspring sections are formed separately and have adjacent ends which insaid normal position are spaced apart but are movable intoload-supporting relation to transmit forces therebetween in saidoverload position, said shoulder means including a first stop shouldercarried by said end of one of said spring sections, and a second stopshoulder engageable by said first stop shoulder after predeterminedcompression of said soft spring section to prevent further compressionthereof and transmit load forces between said masses directly throughonly said stiff spring section.
 7. Overload apparatus as recited inclaim 1 in which said two spring sections are formed separately and havefirst ends received in load-supporting relation with respect to said twomasses respectively, said sections having second ends which in saidnormal position are spaced apart but are moveable into load-supportingrelation to transmit forces therebetween in said overload position,there being a first stop shoulder carried by said second end of one ofsaid spring sections, and a second stop shoulder engageable by saidfirst stop shoulder after predetermined elevation of said sprung massabove said normal position to yieldingly resist further relativeelevation of said sprung mass by the force of said stiff spring section.8. Overload apparatus as recited in claim 1 in which said stiff springsection has a first end secured in fixed position to one of said masses,said shoulder means including a shoulder at the opposite end of saidstiff spring section, and an additional shoulder carried by the othermass and engageable by said first shoulder in force transmittingrelation after said pRedetermined relative movement of said twoshoulders.
 9. Overload apparatus as recited in claim 1 in which saidstiff spring section has a first end connected in fixed position to oneof said masses and has a second end which in said normal position is outof load transmitting relation with said soft spring section, but isrelatively movable into such load-transmitting relation in said overloadposition, said shoulder means including a shoulder structure carried bysaid second end of said stiff section and engageable with two additionalshoulders carried by the other mass to limit relative movement of saidsecond end of the stiff section both upwardly and downwardly. 10.Overload apparatus as recited in claim 9 including a shock absorberextending vertically within said spring sections and connected atopposite ends to said two masses respectively, and means mounting saidadditional shoulders at spaced locations on said shock absorber. 11.Overload apparatus as recited in claim 1 including means securing afirst end of said stiff spring section fixedly to one of said masses anda first end of said soft section fixedly to the other mass, saidsections having second ends which in said normal position are out ofload transmitting relation but are movable into such relation in saidoverload position, said shoulder means including a stop shoulderstructure carried by said second end of said stiff spring section, therebeing a shock absorber within the sections and having a cylinder andpiston connectable one to each of said masses, said shoulder meansincluding two stop shoulders carried by said cylinder of the shockabsorber at spaced locations and engageable with said first mentionedstop shoulder structure to transmit forces therefrom directly to thecylinder in two predetermined positions one of which is beneath theposition in which said two spring sections move into load transmittingrelation, and the other of which is above said normal position.
 12. In avehicle having a main suspension system supporting a sprung massresiliently in a predetermined normal position relative to an upsprungmass; overload apparatus including a stiff coil spring section and asofter coil spring section received operatively in series between saidsprung and unsprung masses, said spring sections being ineffective toassist in supporting the sprung mass in said normal position thereof butbeing positioned and constructed to become effective for such support inseries when the sprung mass moves downwardly relative to the unsprungmass to an overload position, there being shoulder means engageable inan elevated relative position of said sprung mass above said normalposition thereof to yieldingly resist further relative elevation of saidsprung mass by the force of said stiff section independently of saidsofter section.